Electromagnetically operated photographic shutter with flashlamp synchronizer



Feb. 26, 1957 w H|LL ELECTROMAGNETICALLY OPERATED PHOTOGRAPHIC SHUTTER WITH FLASHLAMP SYNCHRONIZER Filed May 6, 1953 3 Sheets-Sheet l INVENTOR W/LBUR G. HILL W (1-7 AL..

ATTORNEYS Feb. 26, 1957 w. G. HILL 2,782,698

ELECTROMAGNETICALLY OPERATED PHOTOGRAPHIC SHUTTER WITH FLASHLAMP SYNCHRONIZER Filed May 6, 1953 3 Sheets-Sheet 2 FIG.5

INVENTOR W/LBUR G. H/ L ATTORNEYS Feb. 26, 1957 HILL 2,782,698

W. G. ELECTROMAGNETICALLY OPERATED PHOTOGRAPHIC SHUTTER WITH FLASHLAMP SYNCHRONIZER Filed May 6, 1953 3 Sheets-Sheet 3 FIG. 6

k '5 m 3; o: g Q U 0 /0 fl zo i0 )0 50 0 /0 2b .20 4b 50 TIME |MILLISECONDS r/M- M/L L/SECONDS Flo w FIG. 9; I I k o /0 2 0- 3 0 4b 50 o 10 a0 TIME MILL/SECONDS, T/ME-M/LL/SECOND F IG. 8 FIG. 10

INVENTOR W/L EUR 6. H/LL ATTORNEYS United. States Patent ELECTROMAGNETICALLY OPERATED PHOTO- GRAPHIC SHUTTER WITH FLASHLAMP SYN* CHRONIZER Wilbur G. Hill, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application May 6, 1953, Serial No. 353,390 1 Claim. (Cl. 95-115) This invention relates to photoflash synchronizing arrangements for photographic shutters and more particularly to automatic time delay operation of shutters in connection with flash bulb ignition.

Photographic flash bulbs consist of a glass vessel generally containing oxygen and aluminum or magnesium in the form of thin wire or foil. with a combustible substance bustion of the aluminum or the fusing of the igniter due is provided and the com-- magnesium is initiated by to electrical current flow supplied from any convenient source, such as a dry bat- Aside from the characteristics of the bulbs, the condi-:

tion of the ignition current source and the contact resist' ance of the switch will also influence the time delay for peak light efiiciency. An older battery will not provideadequate current for instantaneous fusing of the igniter and the switch contacts may have suflicient resistance to lower the current for most eflicient ignition.

Existing synchronizing arrangements require adjust ment by mechanical means to permit the efficient use of bulbs with different time lag or ignition duration. Since the flash bulb lag from the time of closing the circuit to peak intensity is greater than the start of opening of the shutter leaf to maximum opening, the flash contact has to be closed before the shutter is open.

Flash units, synchronized with camera shutters and built within the shutter housing generally operate by a master control element which, after being released, closes the electrical circuit to the bulb, is then delayed or held back by mechanical retarding devices for a predetermined length of time, thereafter being released to actuate the shutter.

Use has also been made of electromagnetic devices such as a solenoid which, after being energized by the flash circuit switch, releases the shutter operating mechanism. However, in either case, the closing of the flash circuit and the timing of the release of the shutter mechanism is controlled by a mechanical delay apparatus which is preset to a predetermined time delay. As a rule, this cannot be varied except in certain of the more expensive cameras which have a selectable delay of either or 5 milliseconds so as to accommodate both types of the most commonly used flash bulbs.

It is the primary object of this invention to provide automatic synchronization of the shutter mechanism for flash bulbs irrespective of their inherent time lag.

t It is a further object of the invention to effect automatic adjustment of the shutter release mechanism and An igniter usually coated most commonly 2,732,698 1 Patented Feb. 26, 1957 to this end means are provided for controlling the release in accordance with the electrical characteristics of the flash bulb.

A particular feature of this invention is that the time delay of shutter operation requires no preset mechanical retard mechanism but is controlled by the electrical current utilized for the ignition of the bulb.

Another feature of this invention is that remote electrical operation of a flash synchronized camera may easily be .eflected in a simple manner without necessitating other than the flash circuit for interconnection between the flash bulb and the camera.

Other objects and features will be apparent from the following description of the invention, defined in particularity in the appended claim, and taken in connection with the accompanying drawings in which:

Fig. 1 is a view, partly in cross section, of a conventional between-the-lens type shutter, in primed position, incorporating the flash synchronizing arrangement;

Fig. 2 is a similar view showing the pertinent component elements of the shutter at the instant of exposure release;

Fig. 3 is a similar view showing the same component elements nearing the end of the exposure period;

Fig. 4 is a perspective view of the movable contactor 0f the flash ignition switch;

Fig. 5 is a schematic circuit of the flash bulb, the switch, the electrical current source and the actuating electromagnet;

Fig. 6 is a modification of the flash synchronizing arrangement applied to a conventional type of shutter;

Fig. 7 is a curve showing the relationship between the magnitude of the ignition current versus time duration of a conventional 20 millisecond flash bulb;

Fig. 8 represents a curve of light intensity versus time duration of a flash bulb having the current characteristics of Fig. 7;

Fig. 9 is a curve showing the magnitude of the ignition current versus time duration of a conventional 5 millisecond bulb, and

Fig. 10 is the corresponding light intensity versus time duration curve of a flash bulb having the current characteristics of Fig. 9.

Referring to the figures, the type of shutter shown in the drawings is chosen, by way of example, to illustrate the modifications required in applying the flash synchronizing arrangement in accordance with the invention. It will be seen that such modifications may easily be made in other types of shutters, without interfering with the primary function thereof.

In all shutters having built-in flash synchronization a switching element must be provided which is actuated upon shutterrelease so as to complete the circuit between the flash bulb and the particular source used for its ignition. This switching element may be connected to any desired moving part of the shutter. However, it is standard practice to use the master member which controls all the interacting components of the shutter in shutters which are pretensioned for operation. Since, as far as the shutter elements are concerned, only the master member plays a part in the flash synchronizationarrangement in accordance with the invention, it is sufficient, for the sake of simplicity, to show only certain of the basic elements of the shutter which are related to the master member. The rest of the shutter mechanism, such as the shutter blade ring, the exposure time device, etc. have accordingly been omitted.

As seen in the various figures, the shutter comprises the casing 12 which houses all the elements, the shutter actuating or master member 13, which is tensioned by the spring 14 when the manual lever 15 which extends from the casing 12 is moved in a clockwise direction. A

catch and; releasemechanism. for the member 13 is provided, consisting of the pawl17 pivoted over the stud 18, having a toe 19 which is operatively interconnected with the release lever 20 pivoted over the stud 21.

The'master member 13 has variousprojections .and notchesfor the control of diversez-component.elements of the shutter. Of these, the projections 23 andj24are adapted to function in connection with the flash synchronizing operation, as will hereinafter be more fully described.

The operation of .theshutter-as to exposure opening is not related to the invention. Consequently, it will sufiice .to. indicate that the shutter leaves 26 are opened and closed when the master member engages the bell crank-27. This occurs-when the lever 20 is depressed so that the pawl 17 is disengaged from the notch 25. Figure 3: shows the beginning of the exposure when the shutter leaves 26 are partly open.

As seen in Figures 1-3, within the shutter casing is an electromagnet or solenoid 30, the plunger arm 31 of which engages the latch 32 which is pivoted over the stud 33. A spring 34- within the solenoid urges the plunger 35 outwardly so as to position the latch 32 away from the projection 23 of the master member 13 when the solenoid is not energized. A switch for the flash ignition comprises the insulated stationary contact and a moving contactor 41. As seen in Figure 4 this is pivoted over the stud 42, extending from the casing 12 andis biased by the spring 43 so that it will return to neutral position after it has been moved, irrespective of the direction.

"A' socket 45 extends from the casing 12 and holds an insulated bushing 46 which carries the contact 47. The winding 29 of the solenoid 30 is in series between the contacts 40 and 47 and the casing provides the common terminal of the flash circuit. As seen in Fig. 6, the flash bulb attachment connects with the shutter by means of a suitable plug 48 which fits into the socket 45 and has an insulated prong which engages the contact 47. In this manner, the battery and the flash bulb 50.are placedin series in the circuit as shown in the simple diagram of Fig. 5. The ground connections indicated represent the casing 12.

Reference should now be had to Figs. 7, 8, 9 and 10. These representthe characteristic curves of two types of flash lamps. It is seen that both types of lamps, irrespective oftheir time lag characteristics,-reach peak light intensity approximately at the time when the current in the igniter circuit ceases. In other words, justabout the time when the current, which .rises steeply. to a definite maximumvalue and is'maintained toradefinitetime duration, falls to zero the peak-intensity of light is reached. Whether the flash bulbs have a 20 millisecond lag'or only a 5 millisecond lag this condition holds true.

Now-then, in'accordance with this invention, use, is made of this characteristic by providing means which retard the shutter operation until the ignition-current falls to zero. In thismanner, automatic synchronization is elfected withany type of flash lamp having the above described characteristics. The simple electromagnetic mechanism as shown performs this function.

Considering the sequence of operation, inFigure lthe shutter is seen primed, ready for release. It is "assumed that a flash bulb-and abattery are connectedsin "the circuit in the conventional manner. *Nowywhen theylever 20 is depressed,ithe master-member :13 is releasedand, powered by the spring 14, will moveina counterclock wisedirection. As thisoccurs, thecontact41, moved by theprojection 24, engages the stationary contact-40 and the ignition circuit is closed. Current through the winding of the solenoid 30 actuates"the plunger 35 which=in turn moves the latch '32. -By the time the mastenmember travels an small fractiomyit is'- arrested' byflthe latch 32 which engages the. notch 1 formed --by "-theprojection 23.

However, as pointed out before, at the instant, nearing peak light intensity, the current drops to zero so that the solenoid 30 is again deenergized, positioning the latch 32 to disengage the projection 23 and the master member 13 is free to complete its shutter operation. The latter condition is shown in Figure 3.

It will become evident that by holding the master member, after release thereof, until current flow in the flash ignition circuit substantially ceases, automatic synchronization is effected irrespective of the time lag which the flash bulb inherently possesses. The longer this lag, the longer the solenoid 30 becomes energized .and correspondingly the master member 13 isheld back for a longer time period. On the other hand, with flash bulbs of shorter time lag, the hold back time of the master member becomes shorter. In practice, this will be effective for flash bulbs having a time lag of 5 milliseconds or more which is within the mechanical inertia limits of the component elements.

Without utilizing a flash lamp, the shutter functions in a normal manner without retarding the master member after the release lever 20 is depressed, there being no circuit completed to the solenoid. This remains deenergized so that the latch 32 remains stationary in the off position and will not engage the projection 23 of the master member 13.

The modification shown in Fig. '6 is based on the same principle except that the shutter release and retard mechanisms are combined into one operating unit; The notch 25 and the projection 23 of the master member 13 are so displaced as to be disengaged for the releasing and subsequently engaged for the retarding operation, by the actuating lever 51. The. latter is of elongated shape; it pivots-overthestud 52 and atone end extends into a detent 53 which is engaged by the plunger arm 31 of the solenoid 30. At the other end, the lever 51 isformed into a latch 54 adapted to engage the projection 23 when pulled down by the solenoid 30. A spring 56 biases the lever 51 into position to engagethe notch, 25 of the master member 13,.and also performs the function of the spring 34, incorporated in the-solenoid 30 in the structure shown in Figs. 1, 2 and 3.

The release lever 20 is pivoted on the stud 21 and has a cam portion57 which engages the latch ,end of the lever 51 so as to lift/the latterand' thereby move the .detent portion 53 away from then0tch25. ,The spring.59 provides' for the return of the release lever 20 to inactive position.

Upon priming the. shutterby moving the lever 15 and thereby. the master member 13- against the spring .14, the engagement of the detent 53 of the lever 51 with the notch 25 will holdthe master member 13. The release of this engagement-may be effected either electrically by the solenoid 30, upon being energized by current from the battery 49, or manually by the release lever 20, as the case may be. When-flash'exposure is to be used the circuit for actuating the solenoid 30 'maybe completed by a simple switch incorporated'into the flash bulb assembly. This ,is shown by the .springcontact 58 within the casing 60 of the flash bulb 50. A manual push button 61 aflixedto the spring contact 58 when depressed effects engagement with the.shell.62 of the flash bulb 50, thereby. completing the circuit from the battery in series with, the igniter 63v over the leads64 and. 6 5,..througl1 connector 48 to the solenoid. 30. .{ASflllS occurs, the plunger arm 31ispulledin, the.;detent. 53;is disengagedfrom the notch :25 andthe master member13 is free to. moveincounterclockwisedirection. .The lowering of the detent 53 of the lever 51 simultaneously raises the other end of this lever sothat the latch 54.-wi1l.engage the projection 23 after-the master member .13 has moved a small distance. Thus, the master'member 13:is retarded until such time as the solenoid is deenergized ZThe latch 54=of-lever 51 is then movedout ofengagementwith the projection 23 by the spring 56 and the master member is free to complete the exposure operation.

As stated before, the currcnt flow abruptly ceases the instant before peak light intensity of the flash bulb, so that the master member 13 is retarded only until there is no current flow in the circni. The flash synchronization feature in the modification described above is the same as in the shutter illustrated in Figs. 1, 2 and 3 but, in addition, the release function may also be effected by the current in the circuit. This is particularly advantageous When flash bulbs are placed at a distance from the camera so that shutter operation may be controlled remotely Without any other electrical interconnection than normally necessary for flash light operation.

When the shutter is used Without flash ignition, the manual release lever 29 provides for normal operation. It should be noted that the cam portion 57 of the release 20 is so dimensioned that it will lift the lever 51 sufficiently to disengage the detent 53 from the master member 13, but not as far as to cause the latch 54 to engage the projection 23. In other Words, in ordinary, manual use of the shutter, no retard of the master member 13 is eifected. Only when the lever 51 is operated by the solenoid 30 is the displacement such as to provide engagemerit of the latch 54 with the projection 23 and assure delayed opening of the shutter until the flash bulb has reached near peak light intensity.

I claim:

In a photographic shutter, a tensionable master member having a notch and a projection spaced therefrom, a pivotally supported actuating lever comprising a detent por tion adapted to engage said notch upon tensioning said master member and a latch portion adapted to engage said projection upon cornpicte pivotal movement of said actuating lever, manual means for releasing said master member comprising a release lever operable to engage said actuating lever eifecting movement thereof to a limited extent so that the said detent portion clears said notch Without said latch portion engaging said projection and an automatic synchronizing arrangement for operation with flash bulbs of the type having an igniter fusible by electric current comprising an ignition current source, a circuit connecting said source with the igniter including, in series, a switch and an electromagnet, said actuating lever being moved by said electromagnet when energized by closure of: said switch to the full extent of its pivotal movement so that said latch portion engages said projection, holding said master member until said magnet is de-energized due to fusion of said igniter.

References Cited in the file of this patent UNITED STATES PATENTS 2,108,246 Aiken Feb. 15, 1938 2,275,221 Goldring Mar. 3, 1942 2,344,645 SchWarZ Mar. 21, 1944 FOREIGN PATENTS 395,040 Great Britain July 13, 1933 462,953 Great Britain Mar. 18, 1937 

